diff --git a/config/application.rb b/config/application.rb
index 1b22feb12..5e93df122 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -33,6 +33,8 @@ module RedmineApp
     config.active_record.store_full_sti_class = true
     config.active_record.default_timezone = :local
     config.active_record.yaml_column_permitted_classes = [
+      Date,
+      Time,
       Symbol,
       ActiveSupport::HashWithIndifferentAccess,
       ActionController::Parameters